四分律比丘含注戒本 3.199

3.199

佛在舍衛。居士設食。六群得少，比座分多，語居士言：「汝今請僧，自恣多少。居士有愛。」報言：「我等與。」比丘舉過。佛因制戒。

The Buddha was in Śrāvastī. A householder prepared food. The group of six received little, while the neighboring seats received much. They said to the householder: "Now that you invite the saṃgha, you arbitrarily give more or less. The householder has favoritism." He replied: "We gave [evenly]." The bhikṣus brought up the fault, and the Buddha consequently formulated the precept.